Logical Reasoning

PT130 · S3 · Q11 Scientists have long thought that omega-3

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Scientists have long thought that omega-3 fatty acids in fish oil tend to lower blood cholesterol and strongly suspected that a diet that includes a modest amount of fish would provide substantial health benefits.

Conclusion

Omega-3’s from fish tend to lower cholesterol, and a diet with a good amount of fish would have a lot of health benefits.

Evidence

A study found that middle-aged people who ate fish twice a week were less likely to get heart disease than those who didn’t eat fish.

Evaluation

The evidence is a correlation, the most famous of all LSAT’s Curious Facts. Why is there a correlation in this study between eating fish and having lower risk of heart disease? The author believes the Causal Explanation for it is that fish contain Omega-3’s, which lower cholesterol, thereby lowering risk of heart disease.

LSAT usually wants us to object to this line of reasoning by considering alternative explanations. Necessary Assumption provides missing links or defends against objections. So the author is assuming that something else is not the real reason the fish group had lower risk of heart disease.

There are also some language shifts that could create bridge assumptions: “eating fish twice a week” = “a diet with a modest amount of fish”? “lowering blood cholesterol” = “lowering risk of heart disease”?

Goal

Correct answer will probably rule out an alternate causal explanation, but it may provide a missing link for either term shift.

11.

Which one of the following is an assumption required by the argument?

  1. The test subjects in the

    Out of Scope: “vegetarians”

    If we negate this, and we say the no-fish group were vegetarians, does that explain why they have a higher rate of heart disease than the fish group? Not unless we think vegetarianism increases your risk of heart disease, which is not a common sense idea.

    1% picked this

  2. The test subjects in the

    Opposite

    If we negate this, it would strengthen somewhat. If the fish-eating group has a diet that, besides the fish, would incline them toward heart disease, yet they’re 30% less likely to get heart disease than non-fish-eaters, then that makes it seem like eating the fish is having a huge effect on lowering their heart disease risk, which strengthens the author’s conclusion that eating fish has health benefits.

    29% picked this

  3. The test subjects in the

    Unclear Impact

    This is tempting, but ultimately D has stronger impact. Eating red meat has a fairly common sense association with increased risk of heart disease, so we might be thinking an alternate explanation for why the non-fish-eaters had a higher risk of heart disease is not their lack of fish but their abundance of red meat. When we compare C and D and ask ourselves, “Which one is a more compelling reason for why one group had lower risk of heart disease: because they ate significantly less red meat, or because they were significantly more engaged in activities known to augment cardiorespiratory health?”, the latter has to win because it’s known to augment heart health.

    2% picked this

  4. Correct

    The test subjects in the

    Why this is right

    If we negate this, it offers a compelling alternate explanation for why the fish-eaters had lower risk of heart disease: way more of them were regularly engaged in activities that are known to help your heart and lung health. When Necessary Assumption intersects with Causal arguments, anticipate Defender answers that rule out an alternate explanation.

    Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.

    65% picked this

  5. The test subjects in the

    Opposite

    If we negate this, then the fish-eating group was more likely to be sedentary. There’s a bit of a common sense link between sedentary lifestyles and higher risks of heart disease. Thus, this answer would be like B, in that negating the answer means that the fish-eating group starts off at a comparative disadvantage to the non-fish-eating group in terms of heart health. We want an alternate explanation that explains why the fish-eating group starts off at a comparative (30%) advantage to the non-fish-eating group, so that we don’t have to credit eating fish with providing that advantage.

    2% picked this

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